In a thread storing and feeding device known from CH-PS No. 381,622, a storage drum is rotated by a drive motor through a belt drive transmission. The storage drum transmits the drive to a feeding body rotatably mounted on a support member determining the eccentricity and inclination of its axis of rotation with respect to that of the storage drum. To this effect the support member is mounted for pivotal movement about two pivot pins extending perpendicular to the storage drum axis. Through a pin-and-slot arrangement the support member is operatively connected to a two-armed lever mounted for rotation about a stationary axis. The arm of said lever facing towards the drive input side of the device cooperates with a pretensioned compression spring urging the lever and thus the feeding body towards the position of greatest inclination of the feeding body axis. The said arm is further pivotally connected to a pair of linkage members operatively connected to stationary switches. The switches control said drive motor in such a manner that a decrease of the inclination of the feeding body causes the rotational speed of the storage drum to be decreased until the thread supply is consumed to such a degree that its wrapping force is no longer sufficient to prevent the feeding body from assuming its inclined position. As the inclination of the feeding body is thus again increased, the drive motor rotates the storage drum at a higher speed until finally the thread supply has grown to such a degree that its wrapping force becomes sufficient to again decrease the inclination of the feeding body. This known device requires a highly complicated structural arrangement for transmitting the movements of the feeding body to the switches for causing the latter to control the speed of the drive motor. In addition, this device is of considerable length and unsuitably heavy. There are a great number of pivot connections and other friction points requiring frequent maintenance and subject to contamination. Finally, the device requires a separate drive motor.
It is an object of the present invention to provide a thread storing and feeding device which is of simple and compact construction, reliable in operation and additionally permits the rotational drive to be operated at constant speed.
According to the solution provided by this invention, a device of the type indicated above requires only very few and simple components for the speed control of the storage body. The drive shaft can be rotated at constant speed. The effective rotational speed of the storage body is determined by the engagement of drive transmitting friction linings which during normal operation assume an equilibrium position with a substantially continuous slip therebetween. Since the other bar drum due to its movable mounting is directly responsible for the speed control, the speed will always be accurately controlled in conformity with the instantaneous amount of the thread supply, i.e. with the wrapping force exerted thereby. A further advantage is offered by the constant speed operation of the rotary drive. The friction surfaces are subjected to a self-cleaning effect and may be very durable. The device is of compact and low-weight construction.
From DE-AS No. 12 58 809 there is indeed known a thread storing and feeding device employing a friction brake for controlling the rotational speed of the storage drum. The principle of operation is completely different, however, as the storage drum is directly coupled to the rotary drive so as to normally rotate at an elevated speed, the friction brake serving to retard the storage drum to the required speed. To this effect, the friction brake causes slippage to occur within the rotary drive, resulting in undesirably high wear therein. This known solution is of extremely complicated construction, in that the amount of the instantaneous thread supply is scanned by pivot levers effective to shift the storage drum via a linkage mechanism until the friction brake is actuated. According to this solution, moreover, the storage drum surface is at the same time formed by the feeding body surface.
A further thread storing and feeding device is also known from GB-PS No. 2,069,016, according to which a friction clutch is disposed betwwen the rotary drive and the storage drum. In this construction the underside of a drive disk of the rotary drive carries a clutch surface cooperating with a second clutch surface disposed on the end face of the storage disk in conformity with the amount of thread stored on the storage drum. The storage drum is spring-biased towards the engagement position of the clutch surfaces and is moved from the drive disk after a sufficient amount of thread is stored.
In accordance with the present invention the exccentricity and the inclination of the other bar drum axis with respect to the axis of rotation of the storage body must be accurately adjustable in order to enable the other bar drum to perform its feeding function as well as its speed control function. Since however the space within the storage body is relatively restricted and rather inaccessible, an embodiment of this invention is of particular advantage. In this embodiment, other bar drum is rotatably mounted on a carrier plate which itself is mounted for movement on a stationary support against a spring bias whereby the eccentricity of the other bar drum with respect to the rotational axis of the storage body can be displaced over a determined range of movement. The carrier plate requires only little space and may without difficulty be located between other components of the device so that the overall length of the latter is not increased and that its proper function is not disturbed.
A further advantageous embodiment has the carrier plate mounted for limited pivotal movement about a stationary pivot axis which is radially spaced from the axis of the storage body and encloses a small acute angle therewith. According to this embodiment, the mounting of the carrier plate is spaced from the axis of the storage body. Due to its acute angle the pivot axis itself determines the inclination and eccentricity of the rotary axis of the other bar drum. A particularly simple structure for attaining this object is characterized by said pivot axis being defined by a pin secured to a stationary mounting member.
The distance of said pin from the axis of the storage body is preferably greater than the radius of the storage body, and this is of importance for enabling the carrier plate and the other bar drum to accurately respond to changes of the wrapping force of the thread supply and for the adjusting forces resulting therefrom to act through a relatively long lever arm. In practice it has been found advantageous to select the distance of the pin from the radius of the other bar drum in a relationship within the range of 1:1.5 to 1:2.
A further advantageous embodiment of the invention has the carrier plate cooperating with a stop in one pivoting direction and biased by a spring in the other pivoting direction for engagement of the drive-transmitting friction linings with one another. According to this embodiment, the stop member acts exactly opposite to the biasing direction of the spring tending to pivot the carrier plate about its pivot axis.
Since it is in any case customary to provide a certain spacing between the stationary support member of the device and the storage body, this spacing may be profitably employed for mounting the carrier plate therein, so that the tubular projection thereof projects into the storage body. This arrangement also provides for simple assembly and disassembly of the device.
Particularly advantageous with a view to facility of construction is a further embodiment wherein the other bar drum is formed as a hollow cylinder carrying an annular drive-transmitting friction lining on its interior wall surface, and wherein the drive shaft carries a friction wheel at the level of the drive-transmitting friction lining, with a complementary friction lining being located on the outer periphery of the friction wheel and having an outer diameter smaller than the interior diameter of the drive-transmitting friction lining. According to this embodiment, the drive transmitting friction surfaces come into mutual engagement only when it is actually required to rotate the other bar drum. At all other times the other bar drum that is the storage body, will remain stationary as the drive shaft rotates at constant speed.
A further important characteristic is the location of the drive transmitting friction surface closely adjacent the rotary mounting of the other bar drum since this results in a desirably short lever arm between these two portions, enabling the rotary mounting to readily absorb the forces acting thereon.